The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Independent mobility is an important requirement for a person's daily life. Reduction in mobility due to visual impairment leads to severe deterioration in the quality of a person's life. Despite the substantial advances in computer vision and robotics, it is still extremely difficult for the visually impaired to move around independently in a 3D space. Up to date, white cane remains as the most efficient navigational tool to the visually impaired due to its powerful haptic feedback from the local environment and its low cost. However, a white cane has limitations in handling obstacle avoidance and wayfinding of pedestrian mobility. Obstacle avoidance deals with local problems in taking steps safely without bumping into anything, tripping, or falling. Wayfinding refers to global problems of planning and following routes from one point to another while maintaining awareness of current position and heading. A white cane is a low resolution device, i.e., one haptic “datum” per contact point. For obstacle detection and avoidance, it is difficult and time-consuming for the visually impaired to obtain the full picture of an obstacle by assembling haptic data from multiple locations. Also, it may miss an overhung obstacle. With respect to wayfinding, a white cane has a very limited range and it is too nearsighted for path planning. For instance, it may be difficult for the visually impaired to locate a distant doorway/stairway that may be used as a waypoint of a navigational task. A conventional white cane does not have wayfinding function unless the blind traveler uses a GPS. However, GPS does not work or work well in an indoor environment.
The computer vision and robotic technologies can be used to build a Robotic Navigational Device (RND) that replaces or enhances a white cane. The main challenge is that the portability requirement of an RND limits its size, computing power and power supply. These constraints exclude the possibility of adopting the approach of multiple sensors and high-end computers in military robots C[1]. As a result, an RNDs currently only offers very limited navigational aid to the visually impaired.
The RNDs can be classified into three categories: Robotic Wheelchair (RW) C[1, 2, 3], Robotic Guide-Dog (RGD) C[1, 2] and Electronic White Cane (EWC) C[1, 2, 3, 4]. A Portable Robotic Device (PRD) is referred to an RND that can be carried or worn by a person with visual impairment. Much research effort has been devoted to the RW approach in the past several decades. A RW is well suited for a blind person who loses the ability to move. However, a RW gives its user an unpleasant sense of being controlled. Given the reality that the current robotic assistive technology is inadequate for navigation in an unstructured environment, safety concerns will keep the visually impaired away from using RWs for their mobility needs. A RGD is a robotic device that indicates a traversable direction to a visually impaired person and guides him/her to the destination. In this case, the user needs to use his/her ability to move. A RGD can be passive or active. A passive RGD C[5] generates the travel direction to the user by steering its wheel, and the user needs to push the RGD forward. A passive RG gives its users a sense of safety that they are controlling the device, but it brings extra workload to users that may cause fatigue. An active RGD C[6], however, generates an additional forward movement that drags the user to the destination. In this way, the RGD can even take on a certain payload without requiring the user to push and thus it does not result in fatigue to the user. However, the robot-centric movement may create uncomfortable feelings in users as they may be dragged around at an uncomfortable pace. An EWC is a handheld/wearable device that detects the obstacle distance in its immediate surrounding. The Nottingham obstacle detector C[7] and the Navbelt C[10] use sonar for obstacle detection. The C-5 laser cane C[8] triangulates the range information using three laser diode transmitters and three photo-diode receivers. The “virtual white cane” C[9] senses range by a baseline triangulation system using a point laser and a miniaturized camera. The user receives multiple range measurements by swinging the device around. In spite of the advantage of portability, this kind of devices usually provides quite limited information to the user due to the limited sensing capability. It is generally impossible for them to perform efficient wayfinding function in a 3D space. Also, a handheld EWC may limit or deny the use of a traditional white cane.
A 3D pose (position and orientation) estimation method for the visually impaired is introduced in C[1] where a sensor package, comprising an Inertial Measurement Unit (IMU) and a 2D laser scanner, is mounted on a white cane to track its pose. The white cane's pose is estimated by integrating the IMU measurements over time and updated by the extended Kalman filter using the straight-line features extracted from the laser scans. The method requires a known map of the indoor environment to compute the intersection of the laser-scan plane and the structural planes of the environment. The use of a 2D laser scanner is still not sufficient for providing details and dimension of environment.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.